AU2010200745B2 - A method for arsenic removal and phosphorous removal out of iron-containing material - Google Patents

Abstract

A method for arsenic removal and phosphorous removal out of an iron-containing material in accordance with the present invention relates to both mining & metallurgical and metallurgical industries, and, more specifically, to the physico-chemical methods of the preparation of iron ore, iron and manganese ores, 3 iron and titanium ores, manganese ores, and other ores, concentrates, sponge iron, prereduced pellets, bloom for the purpose of improving quality owing to an increase in an iron content of the iron-containing material and the removal of undesirable impurities out of it, first of all, arsenic and phosphorous and of isolating valuable impurities, first of all, vanadium. The task to be solved with the present invention is to increase an iron content of the resulting product paralleled with a reduction in an arsenic content and phosphorous content thereof down to the specification values, a reduction in process duration, a decrease in alkaline reagent consumption, and a reduction in cost. l1 Iron-containing material NaCI NaOH Water Milling Gravity separation Weak suspension of disperse Strong suspension of iron-containing admixtures material Filtering 1 Filtering 1 Strong NaCl solution filtrate .fltrate Strong NaOH solution Washing 1 Washing 1 Service water Acidulous NaCl Seawater solution E Washing 2 Washing 2 Tails to dump Washing 4 Service water Seawater Washing 3 Removal of AS P V Zn compounds Washing Iron-containing concentrate (Fe=66-95%, As<0.1%, P<0.15%) Strong NaCI solution for recirculation Fig.1

Description

Regulation 3.2 AUSTRALIA PATENTS ACT, 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant: CLOSED JOINT STOCK COMPANY "DONETSKSTEEL" IRON AND STEEL WORKS" Actual Inventors: Kovzun IGOR, Protsenko IRYNA, Ulberg ZOYA, Filatov YURIY, Ilyashov MYKHAILO, Volovyk VOLODYMYR, and Youshkov YEVGENIY Address for service in A J PARK, Level 11, 60 Marcus Clarke Street, Canberra ACT Australia: 2601, Australia Invention Title: A METHOD FOR ARSENIC REMOVAL AND PHOSPHOROUS REMOVAL OUT OF IRON CONTAINING MATERIAL The following statement is a full description of this invention, including the best method of performing it known to us. 3563/24270941 DOC 2 A METHOD FOR ARSENIC REMOVAL AND PHOSPHOROUS REMOVAL OUT OF IRON-CONTAINING MATERIAL The invention relates to the metallurgy and mining field and the metallurgy field and, more specifically, to the physico-chemical methods of the preparation of iron ore, iron and manganese ores, iron and titanium ores, iron and chrome ores, manganese ores, and other ores, concentrates, sponge iron, prereduced pellets, bloom for the purpose of improving quality owing to the rise of iron content in the iron-containing material and the removal of undesirable impurities, first of all, arsenic and phosphorous and owing to the isolation of valuable impurities, first of all, vanadium. Iron-containing materials used in the industry, for example, in a blast-furnace melting, steel-smelting process are beneficiated to produce concentrates which contain up to 71% of iron, up to 0.15% of arsenic, and up to 0.25% of phosphorous [Ye. F. Vegman (ed.), Blast-Furnace Production, Reference-book, Vol. 1, Ore Preparation and Blast-furnace Process, Moscow, Metallurgy, 1989, p. 496]. Among various iron-containing materials which must be subjected to beneficiation and impurity removal, iron ores with a relatively low iron content (up to 35%) are of the greatest interest. The specific weight of such ores increases continuously in conjunction with the depletion of rich ore reserves and, for the time being, accounts for 20%. Such iron ores include sedimentary ores of marine peloid origin this offering a substantial advantage: a low cost of their extraction. In Ukraine, these are the ores of the Kerch Iron Ore Deposit which contain between 37% and 39% of iron, between 15% and 35% of silicates, up to 1% of phosphorous, up to 0.2% of arsenic, and up to 0.1% of vanadium, as well as up to 4.6% of manganese and other alloying elements; the ores of the Kremenchuk Deposit which contain between 34% and 58% of iron, between 13% and 43% of silicates, the admixtures of phosphorous, arsenic, and sulfur; and ores near the Sea of Azov. In Russia, such ores include the ores of the Tula Deposit, the Lisakovsk Deposit, the Angara-Ilim Deposits, and other iron ore deposits. In Kazakhstan, many iron ore deposits of a sedimentary metamorphized origin also have elevated levels of phosphorous and arsenic. Similar iron ore deposits occur in other counties as well (Australia, China, India, and Canada). Processing such ores constitutes, therefore, while a complicated but an actual problem, and it justifies itself thanks to a relative simplicity of their extraction, mostly, by open-pit mining. In conjunction with this, chemical technologies of processing such complex iron containing materials are used not only in the nonferrous metallurgy but also in the ferrous metallurgy. Known from the state of the art is a method for processing iron-containing materials wherein ore roasted crushed and milled ore is treated with a diluted acid solution at high solid phase-to-liquid phase ratios (S:L) and with a significant duration of process (up to 25 hours), and then undesirable impurities are extracted by the ion-exchange method [French Patent No. 1,505,100, Cl. C22B 3/06, published in 1963]. The disadvantages of this prior art method are a low extraction of impurities, a long duration of leaching, and large quantity of the liquid phase which reduces the process productivity and increases cost. Known from the state of the art is a method for impurity removal out of ore by an oxidizing roasting at between 800'C and 1000'C for 1 hour, by leaching with a 49% sulfuric acid or nitric acid at S:L=l:1-1:2 at between 20'C and 50'C for between 2 hours and 3 hours [Russian Patent No. 2 184 158, Cl. C22Bl/1 1, published on 27.06.2002]. The disadvantages of this prior art method include, in addition to high losses of iron (of up to 4% to 8%) and acid, a chemical corrosiveness of solutions and a low arsenic extraction because of the formation of iron arsenates sparingly soluble in a 49% acid. Known from the state of the art is a method for leaching arsenic and phosphorous out of ore roasted at between 500'C and 600'C for between 1 hour and 1.5 hours with a diluted sulfuric acid at elevated temperatures (between 60'C and 80'C), at S:L=1:3-1:5 and with a process duration of between 2 hours and 3 hours [R.D. Dukino, V. M. England. Phosphorous in Iron Ores of the Hamersley Range, the Australian Institute of Mining and Metallurgy (AusIMM) 1977, No. 5, pp.197-202]. The disadvantages of this prior art method include is a low extraction of arsenic and phosphorous and a substantial consumption of the alkali solution.

4 Known from the state of the art is a method for extracting undesirable impurities out of iron ore by means of the treatment of an iron-containing material with a 40% to 50% solution of alkali in autoclaves at between 125'C and 140'C [The 8 th International Congress for the Beneficiation of Minerals, Vol. 2, Leningrad, 1969]. This prior art method requires, however, a complicated hardware, high levels of an aggressive alkali, as well as significant volumes of water for washing it all these complicating solution recovery and increasing cost. The most similar to a method in accordance with the present invention is a method for arsenic removal and phosphorous removal out of iron-containing material, the method comprising: iron-containing material milling in a mill; then leaching arsenic and phosphorous with a 2% alkaline solution at S:L=1:10 and for about 48 hours [T. S. Syrtlanova et al. Proceedings of the Siberian Division of the Academy of Sciences of the USSR, Chemical Science Series, 1979, edn. 3, No. 7, pp.50-55]. This prior art method, however, firstly, may only be used for sulfide ores with between 0.22% and 1.5% of arsenic remaining in the leached material while its content of, for example, iron-containing ores does not exceed 0.1% to 0.2%; secondly, at a high S:L ratio, an alkali consumption accounts for up to 20% of ore weight; thirdly, the process is long-lasing and an iron content of the iron-containing materials does not increase after treatment with alkali; and a significant cost. Accordingly, the task to be solved with the present invention is to improve a method for arsenic removal and phosphorous removal out of an iron-containing material wherein a preliminary milling of an iron-containing material in a concentrated alkali solution of sodium chloride, the following gravity separation of a solid iron-containing material and a suspension of disperse admixtures; the separation of the iron-containing material from the liquid phase; and washing the solid phase with a concentrated acid solution of sodium chloride ensure an increase in iron content of the product and a reduction in an arsenic content and phosphorous content thereof down to the specification values this ensuring a reduction in a process duration, a reduction in an arsenic content and phosphorous content of an iron-containing residue, a decrease in an alkaline reagent consumption, a reduction in its losses, and a reduction in cost.

5 The set task is solved by a method for arsenic removal and phosphorous removal out of an iron-containing material, the method comprising the milling of the iron-containing material and its leaching, wherein, in accordance with the present invention, the following differences are provided for: - A preliminary milling of the iron-containing material in a concentrated alkali solution of sodium chloride to obtain a suspension; - The gravity separation of the resulting suspension into a solid phase and a suspension of disperse admixtures; - The separation of the solid phase of the iron-containing material from the liquid phase; and - Washing the solid phase with a concentrated acid solution of sodium chloride. The iron-containing material is also milled in the concentrated alkali solution of sodium chloride of pH=1 1-12, S:L=1:1.25; the sodium chloride concentration of water is maintained between 15 % w/w and 28 % w/w; the solid phase of the iron-containing material separated from the concentrated alkali solution of sodium chloride is washed with a concentrated aqueous solution of sodium chloride in the quantity which is equal to a moisture content of the solid iron-containing material; and the iron-containing material is washed with the concentrated acid solution of sodium chloride of pH=1-2 at 1:1.25. The essence of the present invention will now be explained with the reference to a process flow diagram of arsenic removal and phosphorous removal out of the iron containing material simultaneously with the beneficiation thereof shown in Fig. 1. The method in accordance with the present invention may be practiced as follows. Charged in a mill are an iron-containing material, water, sodium chloride, and sodium hydroxide the latter being introduced in a quantity sufficient to maintain pH between 11 and 12. The iron-containing material is milled to obtain the particles of the beneficiated iron-containing material (hematite, wustite, metallic iron) of between 0.063 mm and 0.25 mm fractions and the particles of admixtures (silicates, carbonates, fine carbon and 6 iron oxides) of minus 0.063 mm fraction. Under such conditions, as the inventors of this invention have established, there occur the leaching, out of the iron-containing material, and the following dissolution of the arsenic compounds and phosphorous compounds in the concentrated alkali solution of NaCl. Paralleled therewith, other alkali-soluble compounds, for example, vanadium, zinc, are also dissolved. The suspension obtained after milling is subjected to the gravity separation (jigging), thereby dense particles of hematite, wustite, and metallic iron are concentrated in a coarse, readily precipitating precipitate this making it possible to increase an iron content calculated with the reference to metallic from between about 35 % w/w and about 45 % w/w of the initial material up to between about 65 % w/w and about 95 % w/w of the beneficiated iron-containing material. Paralleled therewith, the arsenic content and the phosphorous content of the latter each is reduced from between 0.2% and 0.3% down to between 0.05% and 0.1% As and from between 0.5% and 1% down to between 0.2% and 0

.

2 5 % P, respectively, as well as the other alkali-soluble admixtures are removed. This is a result of that, as the inventors of this invention have established, with the involvement of the concentrated alkali solution of sodium chloride in the presence of insignificant admixtures of alkali (between 0.1% and 0.5% of the weight of sodium chloride), there are formed stable fine suspensions (colloidal solutions) of iron ore admixtures which have a low thickness, i.e., of silicates, carbonates, carbon, hydrated iron oxides, phosphates, and arsenates. At the same time, rich-in-iron materials (hematite, wustite, sponge iron, bloom) are contained in the suspension in the form of coarse particles and are readily subjected to the gravity separation (jigging). The beneficiated precipitate of the iron-containing material is separated from any liquid phase residues, for example, by filtering, and is washed with a concentrated solution of sodium chloride which is taken in the quantity which is equal to a moisture content of the iron-containing material. Under such conditions, the concentrated solution of sodium chloride displaces substantially completely a low-alkali solution of sodium chloride in the iron-containing material precipitate. As the inventors of this invention have established, under such conditions, no reduction in the solubility of phosphates and arsenates which are contained in the solution takes place, and these are removed out of the solution. In the event that clean water is employed to wash the iron-containing 7 material, the solubility of phosphates and arsenates reduces 5 to 10 times as much, and fine nanoparticles formed of phosphates and arsenates are sorbed on the surface of the iron-containing material thereby contaminating the same. The iron-containing material is washed with a low-acid concentrated solution of sodium chloride of pH=1-2 at S:L=1:1-1.25 since, as the inventors of this invention have established, under such conditions, phosphates as well as insignificant admixtures of arsenates and vanadates partially sorbed by the surface of the iron-containing material are dissolved in the low-acid solution and are removed by filtering. This improves additionally the degree of the removal of the compounds of phosphorous, arsenic, and vanadium out of the iron-containing material. It should be noted that substantially no dissolution of iron itself takes place under such conditions. A level of sodium chloride of its concentrated solutions is maintained between 15 % w/w and 28 % w/w of NaCl, since, as the inventors of this invention have established, in a low-acid solution at pH=11-12, a high concentration of sodium ions ensures the same conditions of leaching phosphates and arsenates out of an iron containing material as a NaOH solution with a concentration of between 15 % w/w and 28 % w/w. Examples of practicing the method in accordance with the present invention using, as the starting material, a sedimentary ore from the Kiz-Aul Deposit of the Kerch Iron Ore Basin will be now described. This ore has the following chemistry (% w/w): SiO 2 =7.1; A1 2 0 3 =4.1; CaO=4.5; Mn=12.3; Fe=39.1; As=0.33; P=0.58; and V=0.05. This ore was heat-treated by the direct iron reduction method [P. P. Arsentyev, V.V. Yakovlev, M.G. Krasheninnikov, et al., General Metallurgy, Moscow, Metallurgy, 1986, p. 360]. EXAMPLE 1 1160 g of prereduced iron ore pellets were divided into the following fractions: Fraction 1 (-0.25 mm) of 221 g in weight containing (% w/w): (Fe+Mn)=94.8; CaO-SiO 2 =4.2; V=0. 15; Y=0. 17; As=0. 15.

8 Fraction 2 (-0.25+0.08 mm) of 519 g in weight containing (% w/w): (Fe+Mn)=61.4; CaO-SiO 2 =3.7; SiO 2 =8.1; A1 2 0 3 =5.4; V=0.05; Y=0.07; Ni=O.11; As=0.22; Zr--0.05. Fraction 3 (-0.08 mm) of 420 g in weight which is waste and contains (% w/w): (Fe+Mn)=12.7; As=0.35; silicates and coke being the balance. Fraction 2 of 519 g in weight was transferred to a steel ball mill to where there were added 248 g off sodium chloride, 770 g of water and 3 g of caustic soda (sodium hydroxide) to a solution pH = 12 (S:L=1:1, a concentration of NaCl=24.36 % w/w) and was milled for about 2 hours; the resulting suspension was separated from the balls and filtered to a humidity of 30.4 % w/w; the filter residue was washed with 158 g of a NaCl solution of 24.36 % w/w in concentration (the quantity of the solution was equal to the moisture content of the filter solid residue). The filter residue was washed with 519 g of a NaCl solution of 24.36 % w/w in concentration with 0.5 % w/w of H 2

SO

4 this ensuring a solution pH=12. The filtrates were mixed and utilized for isolating solid compounds of arsenic, phosphorous, and vanadium out of them. The filter residue was washed with 519 g and dried up. Following decantation, 421 g of iron ore concentrate were obtained which concentrate contained (% w/w): (Fe+Mn)=69.8; As=0.07; P=0.13. EXAMPLE 2 1000 g of iron-containing pellets were transferred to a steel ball mill. 250 g of NaCl were dissolved in 1000 g of water. To the resulting 20% solution of NaCl, 5 g of NaOH were added to achieve pH=12. An alkali solution of sodium chloride was added to the mill the iron-containing pellets (S:L=1:1.25). The solid material was milled for about 2 hours. The resulting suspension was separated from the solution. A residue of a humidity of 29.1 % w/w was washed with a 20% solution of NaCl in a quantity of 291 g and then with water in a quantity of 1000 g. The solid residue was separated from suspended particles and dried up. 621 g of iron ore concentrate were obtained which contained (% w/w): (Fe+Mn)=67. 1; Y=0. 1; V=0. 1; Ni=0. 1; As=0.08; P=0. 16.

9 EXAMPLE 3 1000 g of iron ore powder were mixed with a coke breeze; the resulting mixture was kept under reducing conditions of an additional iron reduction at 1300 0 C. The resulting cake in a quantity of 1105 g was subjected to a dry milling and screening through sieve No. 0063. The following were obtained: 1. 606 g of iron-containing material in the form of granules of -3+0.5 mm and dust of -0.08 mm (% w/w): (Fe+Mn)=89.8; As=0.23; P=0.48; 2. 591 g of silicate and slag waste of a -0.08-mm fraction containing (Fe+Mn)=12.7%; and 3. 8 g of irretrievable losses during separation. 606 g of iron-containing material in the form of granules were transferred to a ball mill to where there were added 606 g of water, 180 g of NaCl and 3 g of NaOH and were milled for about 2 hours. A suspension of solid particles of a -0.38-mm fraction was obtained and filtered. A solid residue in a quantity of 179 g of a humidity 29.5% was washed with a 20% solution of NaCl of pH=1.5, and then was washed with 606 g of water. The resulting residue was mixed with 1200 g of water and was subjected to the gravity separation. 25 g of a-0.08-mm fraction were removed along with the suspension and a heavy precipitate was separated from water and dried up. 577 g of an iron powder of -0.38-mm +0.08-mm fractions were obtained which powder contained (% w/w): (Fe+Mn)=94.1; As=0.06; P=0.06; S=0.01; CaO=1.1;SiO 2 =0.9; A1 2 03=0.7; C=3.2. Other examples of practicing the method of arsenic removal and phosphorous removal out of the iron-containing material in accordance with the present invention are set forth in Table 1 where an example (No. 0) of practicing the method for arsenic removal and phosphorous removal out of an iron-containing material in accordance with the prototype is also presented.

10 Table 1 Example NaCl, % NaOH, S:L Process Content of Solid Residue, % No. % Duration, w/w Hours Fe+Mn As P 0 0 2 1:10 48 39.3 0.31 0.55 1 24.36 0,39 1:1 2 69.8 0.07 0.13 2 20.0 0.5 1:1.25 2 67.1 0.08 0.16 3 28.0 0.5 1:1.25 2 68.3 0.07 0.12 4 15.0 0.5 1:1.25 2 65.4 0.13 0.18 5 12.0 0.5 1:1.25 2 54.3 0.19 0.28 Summing up the results set forth in Table 1 above, it may be concluded as follows: 1. The addition of sodium chloride to the leaching solution makes it possible to reduce significantly a process duration paralleled with a reduction in an arsenic content and phosphorous content of the iron-containing residue by between 70% and 85%; 2. The method in accordance with the present invention makes it possible, paralleled with arsenic removal and phosphorous removal, to accomplish the beneficiation of an iron-containing material with respect to metal (Fe+Mn) from 51.3% up to between 65.4% and 94.1%; 3. A low starting alkali level (between 0.4% and 0.5%) makes it possible, including also owing to the recirculation of treated filtrates, to reduce alkaline reagent consumption and to lower alkaline reagent losses 20 to 25 timed as much. The use of the method in accordance with the present invention would make it possible to beneficiate iron ores with a low iron content while reducing their arsenic content and phosphorous content, to shorten the duration and to improve the productivity of the process, to reduce alkaline reagent consumption, and to lower the process cost. The term "comprising" as used in this specification means "consisting at least in part of'. When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

Claims (6)

1. A method for arsenic removal and phosphorous removal out of an iron-containing material, the method comprising: milling of the iron-containing material and its leaching, characterized in that the method comprises preliminary milling of the iron-containing material in a concentrated alkali solution of sodium chloride to obtain a suspension; gravity separation of the resulting suspension into a solid phase of the iron-containing material and a suspension of disperse admixtures; separation of the solid phase of the iron-containing material from a liquid phase; and washing the solid phase with a concentrated acid solution of sodium chloride.

2. The method as claimed in Claim 1, characterized in that the iron-containing material is milled in the concentrated alkali solution of sodium chloride of pl=l 1-12 at S:L =1:1 25.

3. The method as claimed in Claim 1, characterized in that the sodium chloride concentration of water is maintained between 15 % w/w and 28 % w/w,

4. The method as claimed in Claim 1, characterized in that the solid phase of the iron-containing material separated from the concentrated alkali solution of sodium chloride is washed with a concentrated aqueous solution of sodium chloride which is taken in the quantity which is equal to a moisture content of the iron-containing material.

5. The method as claimed in Claim 1, characterized in that the iron-containing material is washed with a concentrated acid solution of sodium chloride of pll=1- 2 at S:L--:1.25.

6. A method for arsenic removal and phosphorous removal out of an iron-containing material, the method substantially as herein described with reference to any embodiment shown in Figure 1. RECEIVED TIME 8. MAR. 23:16 PRINT TIME 8. MAR. 23:19